As techniques have become more sophisticated for locating subterranean reservoirs, wellbores have become more deviated in an effort to extract the hydrocarbons from below the surface. Coiled tubing has become more prevalent in running tools downhole. Even if rigid tubing is used in a deviated wellbore, actuation of downhole tools using rotation becomes difficult. With the downhole tools supported on coiled tubing, rotation is not possible as part of a technique to set or release downhole tools.
Many reservoir treatment procedures require isolation of a specific zone in the wellbore and the application of fluids to the formation in the isolated zone. In order to accomplish this, the zone is generally isolated between a bridge plug located below and a service packer above. A work string is connected to the service packer for access between the two isolation devices so that, for example, the formation can be acidized between the bridge plug and the service packer above. In many situations, the process must be repeated at multiple locations. One technique that has been used in the past where multiple locations need to be isolated is that the lowermost location has an expendable bridge plug set below it and the service packer is run on a work string to define the first zone to be treated. When the next zone needs to be treated, the service packer is removed from the wellbore and another expendable bridge plug is inserted to define the lower portion of the next zone to be isolated. The service packer is then run in the hole again and the next zone is isolated. This process is repeated until all zones to be treated have been isolated in a similar fashion. At the conclusion of the treatment or procedure, the service packer is removed and all the bridge plugs which have been placed in the wellbore are milled out. There are distinct disadvantages in this procedure in that it requires multiple trips in and out of the well with the service packer so that subsequent bridge plugs can be deployed. Each of the bridge plugs must be separately run in the well and ultimately milled out. Thus, improvements to this technique have generally involved reducing the mill-out time for all the bridge plugs that are in the wellbore. One way this has been accomplished is to make the bridge plugs of generally soft, nonmetallic components so that they can be drilled quickly. Typical of such plugs which are designed to be easily drilled out are U.S. Pat. Nos. 5,224,540 and 5,271,468 issued to Halliburton.
Another way to accomplish the goal of servicing discrete portions of a wellbore in one trip is to use a straddle tool which has a pair of packers which can be set and unset as desired. One of the disadvantages of this type of a tool is that the distance between the packing elements on the tool is defined at the surface when the bottomhole assembly is put together. These tools, typically referred to as "wash tools," are illustrated in U.S. Pat. Nos. 4,815,538; 4,279,306; 4,794,989; 5,267,617; 4,962,815; 4,569,396; and 5,456,322.
Another method of isolating and treating zones is accomplished by running a retrievable bridge plug below a service packer. The coupled system is run just below the zone of interest, the bridge plug is set and uncoupled from the service marker. The service packer is then moved up the hole just above the zone and set by rotation and weight to complete the zone isolation. When treatment is complete, the service packer is unset, moved downhole to recouple with the bridge plug, then unset and moved up the hole to repeat the operation.
Service packers and bridge plug systems that individually set with rotation and setdown force are known. These packer/bridge plug combinations have been used in the procedure described above involving one trip to accomplish straddles of different zones. Typical of such packers are the Retrievamatic.RTM. and model G retrievable bridge plug offered by Baker Oil Tools and the RTTS service packer and 3L bridge plug offered by Halliburton. Tension-set packers, involving a rotation and pickup force, are also known. Typical of these are the Baker Oil Tools Model C "Full Bore" service packer and the Model C cup-type bridge plug.
What is desirable and is an object of the present invention is to provide an apparatus and method to allow isolation of zones of various lengths in a wellbore by allowing deployment of isolation devices where desired where the isolation devices are actuated without rotation. Another objective of the present invention is to allow redeployment of the isolation devices in different locations in the wellbore without a trip out of the well. More particularly, where rotation is not possible, the objective is to allow for the deployment and redeployment and separation downhole between the isolation devices, using fluid pressure and/or longitudinal movements only. Yet another objective of the present, when used with a bridge plug and a service packer, is to keep the service packer locked against setting while the bridge plug is being set. Thereafter, when the service packer is separated from the set bridge plug, the act of separation unlocks the service packer, allowing it to be subsequently set on further manipulations when it reaches its desired location in the wellbore. Yet another objective is to allow the boftomhole assembly to be open to circulation during run-in and closed off when the bridge plug is set. The bridge plug can be equalized by reopening a passage therethrough prior to release of the bridge plug. These and other objectives of the present invention will be more apparent to those of skill in the art from a review of the preferred embodiment described below.